Electrostatic telephone-receiving instrument



G. MACE-IE March 31, R931.

ELECTROSTATIC TELEPHONE RECEIVING INSTRUMENT -Filed July 9, 1929 2 Sheets-Sheet l Inventor.- Gd'nkr Havel/e,

March 31,1931 G MACHE 1,799,053

ELECTROSTATIC TELEPHONE RECEIVING INSTRUMENT Filed July 9. 1929 2 Sheets-Sheet 2 Inventor- 9 Gnr Mach;

Patented Mar. 31, 1931 UNITED STATES GI'iNTER MAoHn, or BERLIN, GERMANY ELECTROSTATIC TELEPHONE-RECEIVING INSTRUMENT Application filed July 9, 1929, Serial No. 377,038, and in Germany April 30, 1929. i

This invention relates to electrostatic telephone receiving instruments, and particularly to so-called electrostatic loud speakers.

Such an instrument consists essentially of a d condenser which comprises a fixed electrode and an easily movable electrode to which a direct current potential is applied in conjunction with an alternating potential.

The alternating vpotential sets up electrostatic forces which give rise to attraction between the two electrodes so as to cause the movable electrode to move to and from the fixed electrode. The alteration in capacity due to the relative movement forms the working capacity of the telephone instrument. The alteration in capacity gives rise to a corresponding alteration in air pressure due to the movement of the diaphragm, resulting in the sound output of the instrument. Thus, it is desirable in practice to provide as great a working capacity as possible-in these electrostatic loud speakers.

In practice, however, the working capacity is limited by the spacing apart of the electrodes in the working condition. On the one hand, the distance apart must be chosen sufliciently great in order to render possible large amplitudes of vibration. This, however, cannot be attained incon possible. Furthermore, if the electrodes are spaced widely apart, the necessary drivpotential is increased.

in v %n order to produce the conditions for the greatestpossible working capacity and the of the electrodes is a minimum close to the point at which the surfaces are superimloud speakers.

junction with the conditions necessary for obtaining an effective capacity as great as a satisfactory rolling or posed. The variation in air pressure necessary to give rise to the sound output occurs due to the fact that the air is pressed out laterally due to the fiattening'action of the movable electrode.

Thus, according to the invention, the fixed and movable electrodes are arranged so that the movable electrode is disposed alternately close to and spaced away from the fixed electrode, the arrangement being produced by suitably curving or troughing the fixed or movable electrode in such a way that the rolling or flattening action and the elastic recovery of the movable electrode relatively to the fixed electrode can take place easily. In order that the invention may be readily carried into effect, some examples of ar rangements of the movable and fixed elecf trodes of electrostatic loud speakers in accordance with the invention will be de- 7 scribed with reference to the accompanying drawings, wherein Figures 1 to 3 are enlarged cross-sections of a part of the electrodes of electrostatic Figure 4 is a complete top view of a cylindrically shaped loud speaker in accordance with the invention.

Figure 5 is a diagrammatic top view of a loud speaker composed of five cylinder so parts.

Figure 6 is. a scheme ofthe whole loud speaker arrangement and shows as well a modified form of the loud speaker as the electrical'connections. I

Referring first of all to Figure 1, the fixed electrode a is provided with perforations or slots d arranged in rows. The movable electrode b is placed opposite the fixed electrode but is given the shape of a series of troughlike strips, the central line of each trough merely being separated from the fixed electrode a by a layer of 'solid dielectric a The angle at which two trough-like sections of the the electrostatic forces which come into action when the device is o crating give rise to Eattening efiect with an elastic recovery of the same. The holes or slots d in the fixed electrode a are-armovable electrode 6 meet is so designed that ranged so that they occur opposite the ridges or lines 6 of junction between the troughs of the movable electrode 1).

In Figure 2, a modified construction is shown in which the fixed electrode a is shaped with corrugations or trough-like strips. The elastically yielding movable electrode 1) is shaped so that it comes'into contact with the fixed electrode a except for the small distance it is spaced away by the dielectric 6 along the centre lines of the trough-like sections of the fixed electrode a. Of course, both electrodes may be shaped so as to be in the form of corrugated strips or troughs.

The invention may be applied to a loud speaker with a differential drive for the movable electrode. An example of such an arrangement is shown in Figure 3 wherein the movable electrode 3) is placed between two fixed electrodes at and a to which an alternating potential is applied so as to Work in opposition upon the movable electrode 6. The fixed electrode a is as in Figure l with rows of perforations or slots d. The fixed electrode a is'formed as corrugated strips or troughs of a configuration to suit that of the movable electrode 6. The fixed electrode a also has rows of holes or slots d opposite the ridges between successive troughs of the movable electrode 6. It will be notedthat the radius of curvature of the sections of the electrode a is substantially smaller than that of the sections of the movable electrode 1) so that the latter can flatten out or roll out both against the fixed electrode a and the fixed electrode a, although, of course, here also it is separated from these electrodes by the insulating or dielectric layer 0.

In the form of the loud speaker as shown in Fig. 4 in a top view, the fixed electrode a has the form of a cylinder. Round this cylinder, there is laid the movable electrode Z) which generally is shaped according to Fig. 1 and composed of corrugated strips or troughs as this was described in connection with Fig. 1. Between the electrodes at and b, the insulating or dielectric layer e is arranged. Upon the outer surface of the movable electrode b, the membrane or diaphragm f is fixed. This diaphragm consists, in the preferred form, of very thin paper. I

The diagrammatic top view of Fig. 5 shows another form of loud speaker according to the invention. In this form, the loud speaker is composed of five single cylinder parts which may be welded or fixed to each other in any suitable manner. The whole apparatus is built up in the way shown in Fig.4.

Still a different form of the loud speaker is shown in Fig. 6. In this form, the fixed electrode (1 forms a relatively small part of a cylinder of large diameter. The electrode a is surrounded by the insulating layer 0 and this layer by the corrugated movable electrode 6, upon which the diaphragm 7 1s expended.

One kind of connection between the loud speaker and the electric apparatus is to be seen from Fig. 6. Between the plug of the accumulator g and the valve h, a throttling winding 15 is interposed. To the connecting line between the winding 2' and the anode, a conductor m is branched off to the electrode a of the loud speaker whereas the electrode 1) is connected to the connecting line at between the plug of the accumulator g and the cathode of the valve h by a conductor 0.

I claim 2-- 1. An electrostatic loud speaking telephone comprising in combination a fixed electrode, a dielectric layer applied to said fixed electrode, a corrugated movable electrode shaped so as alternately to be in contact with said dielectric layer and to be spaced apart from same, and means for applying to said electrodes a direct current potential in conjunction with an alternating potential.

2. An electrostatic loud speaking telephone comprising in combination a fixed electrode formed with rows of apertures, a dielectric layer in contact with said fixed electrode and correspondingly apertured, a corrugated movable electrode shaped so as alternately to contact with said dielectric layer and to be spaced away from same, the spaced-away portions lying opposite the apertures in said fixed electrode, and means for applying to said electrodes a direct current potential in conjunction with an alternating potential.

3. An electrostatic loud speaking telephone comprising in combination a fixed electrode, a dielectric layer in contact therewith, a movable electrode shaped as a series of adjoining corrugated strips, and means for applying to said electrodes a direct current potential in conjunction with an alternatlng current potential.

4. An electrostatic loud speaking telephone comprising a fixed electrode shaped as a series of adjoining corrugated strips with rows of apertures along the junction between said strips, a dielectric layer applied to said electrode on the convex surfaces thereof, a movable electrode also formed as a series of adjoining corrugated strips and in contact with said dielectric layer along the crests of the corrugated strips thereof, and means for applying to said electrodes a direct current potential in conjunction with an alternating potential.

5. An electrostatic loud speaking telephone comprising a fixed electrode formed wlth rows of apertures, a dielectric layer in contact with said fixed electrode, a movable electrode comprising a series of adjoining corrugated strips, a second fixed electrode disposed on the side of said movable electrode remote from said first-mentioned fixed electrode, and comprising a series of adjoining corrugated strips each having a radius of curvature substantially less than that of the corrugations of said movable electrode, and a second dielectric layerinterposed between said movable electrode and said secondnamed fixed electrode, and means for applying: to said electrodes a direct current potential and an alternating potential so as to act in opposition on said movable electrode to afford a (liiferential drive.

6. An electrostatic loud speaking tele hone comprising in combination apair 0 electrodes, a dielectric layer applied to one of said electrodes, one of said electrodes being fixed, the other electrode being movable and being corrugated so as alternately to be adjacent to said fixed electrode and separated therefrom only by the thickness of said dielectric layer and to be spaced apart from said fixed electrode. and means for applying to said electrodes a direct current potential in conjunction with an alternating potential. In testimony whereof I afiix my signature.

GI'JNTER MACHE. 

